Pumping system

ABSTRACT

A pumping arrangement particularly adapted for use to pump mercury from a decomposer to a mercury cell. The novel arrangement permits removal of the impeller, shaft and motor and replacement or inspection without draining the system while significantly reducing the volume of mercury required when compared with prior art pumps. The pumping arrangement provides space for sealing water to be located over the mercury to preclude contact between air and the mercury cell. The simplified pump arrangement eliminates the need for dynamic seals between the pressurized fluid and the atmosphere, as there are no wetted bearings or rubbing parts in the area of the pumping chamber.

United States Patent 1 3,607,705

[72] Inventor James Nagle 3,441,492 4/1969 Fomoni 204/220 20536 Greenwood Drive, Olympia Fields, FOREIGN PATENTS Ill 60461 711,111 61954 G tB tai 204 220 211 Appl. No. 815,909 n [22] Filed Apr. 14, 1969 Primary Exammer.lohn l-l. Mack [45] Patented Se t. 21, 1971 Assistant Examiner-D. R. Valentine Attomey-Robert E. Wagner [54] PUMPING SYSTEM 6 Claims 3 Drawing ABSTRACT: A pumping arrangement particularly adapted [52] U.S.Cl 204/220, f e t pump mercury from a decomposer to a mercury 204/237 cell. The novel arrangement permits removal of the impeller,

[ llll- C221! shaft and motor and replacement or inspection without drain- Bolk ing the system while significantly reducing the volume of mer- [50] Field Of Search 204/219, any required when compared with prior art pumps, The 220, 250, 237 pumping arrangement provides space for sealing water to be [56] Reemm Cited located over the mercury to preclude contact between air and the mercury cell. The simplified pump arrangement eliminates UNITED STATES PATENTS the need for dynamic seals between the pressurized fluid and 1,160,811 11/1915 Acker 1. 204/220X the atmosphere, as there are no wetted hearings or rubbing 3,420,757 1/1969 Friemel et a] 204/220 X pa ts in the a ea of the pumping chamber.

PATENTED SEP21 l97l DIIIIII l INVENTUR JAMES NAGLE ATT'Y.

PUMPING SYSTEM This invention relates to improvements in mercury handling apparatus and, more specifically, relates to a new and improved pumping arrangement particularly adapted for use with a mercury cell.

The chloralkali industry has grown significantly over the past several years because of the increase in demand for these products. One widely used process relies on the use of a brine solution which is flowed with mercury in an electrolizer or cell to generate chlorine with a mercury-sodium amalgam being formed. The amalgam and spent brine are separated after the chlorine is released, with the amalgam going to a decomposer where a caustic is formed, hydrogen is released and the mercury collects in the bottom of the decomposer. The mercury assumes its original pure form and is recirculated back to the cell or electrolizer. The type of mercury cell which has stood the test of time is the horizontal mercury cell which relies on gravity to feed the brine and mercury through the electrolizer or cell. In this type of cell, the mercury flows in a thin sheet across the insulated surface about 2 to 3 millimeters below adjustable graphite anodes. As the brine solution flowing on top of the mercury is decomposed, the sodium (or potassium) is picked up by the mercury forming the amalgam while the chloride is released in the form of chlorine gas. As noted, the amalgam and spent brine are separated with the former being reacted in a decomposer (or denuder) with purified water to form an alkali and hydrogen gas. The mercury returns to it original fonn for recirculation back to the cell.

As can be appreciated, the mercury inventory for such a system remains substantially constant as it functions as a moving electrode and carrier. Mercury costs fluctuate and, at present, are in the range of about $7 to $8 per pound. When considering that the mercury inventory for a plant producing 100 tons of chlorine per day is 88,000 pounds, it can be appreciated that considerable capital is tied up in mercury inventory alone. Allied with this problem is the need for an economical pumping arrangement capable of being removed from the system for maintenance without requiring the entire system to be shut down and drained.

In prior art cell designs, a blister or separate pump tank was attached to or located alongside the decomposer. As the mercury flowed through the activated carbon bed into the bottom of the decomposer, it was gravity-fed into the pump tank where a vertical submerged sump-type pump delivered it back to the mercury cell. This pumping arrangement was acceptable from the standpoint of pumping, however, was undesirable for a number of reasons. A considerable inventory of mercury was required due to the relatively large pump tank which was necessary to physically accommodate the vertically submerged type of pump. As is obvious, the mercury had to be at a level to assure a supply to the pump. In addition, the mercury below the pump and above the bottom of the tank is unavailable for pumping and, hence, needlessly increases the mercury inventory. Replacement, periodic inspection and cleaning of the pump required the discharge line to be separated. When considering that plants having a capacity of any significance have a large number of cells, the additional mercury inventory required by such pumping arrangement is considerable and the coincident cost aspects assume substantial importance. Nevertheless, for want of a satisfactory'altemate, the chloralkali industry has lived with this problem.

The present invention provides a solution to the problem outlined above. A new and improved pumping arrangement is provided particularly adapted for use with horizontal mercury cells and will permit a marked reduction in the total amount of mercury required for each cell with attendant savings. The vertical submerged sump-type pump is eliminated in lieu of the novel tanklike column supporting a pump casing or chamber at its lower end. A drive motor is positioned above the tank column and drives an impeller in the pump chamber through a shaft extending through the center of the tanklike column. A discharge outlet is formed tangentially of the pump chamber containing the impeller is formed in a casing sidewall which is removable as a unit with the impeller. The inlet is in direct axial communication with the tank column. A radial inlet to the tank column permits gravitational inflow of the mercury directly from the bottom of the decomposer to the tank column. Thus, the need for a sump or tank is eliminated.

This unique pump arrangement permits marked reduction in the quantity of mercury required. The tank column is provided with a mild caustic sealing solution over the mercury to isolate the mercury from contact with the air. As a further novel feature, the casing sidewall forming the inlet to the pumping chamber is supported by a shaft column. This permits the shaft, shaft column, pump chamber wall and impeller to be removed expediently as a unit. In this fashion, access is had to the pump chamber without draining the system.

The stationary shaft column permits uniform distribution of the mercury around the shaft and assures that the rotational forces generated by the shaft rotating the impeller will not be imparted to the mercury as it flows toward the inlet. The shaft column also isolates the seal water from the shaft seals located at the top of the column, avoiding deterioration and/or deposit of caustic crystals in the seal. Advantages of the present invention in addition to those stated above will become apparent on consideration of the stated objects and description which follows.

It is an object of this invention to provide a new and improved method and apparatus for handling mercury in conjunction with horizontal mercury cells.

It is a still further object of this invention to provide a new and improved pump design for handling mercury in a mercury cell arrangement which will permit the mercury inventory to be reduced without impairing the cell efficiency.

It is a further object of this invention to provide a new and improved pumping arrangement which is easier to remove for inspection and cleaning.

It is a further object of this invention to avoid the expense and need for a separate tank to accommodate a vertical submerged sump-type pump.

It is a further object of this invention to provide a pump arrangement which is easily removed for cleaning and inspection without draining the system and, thus, eliminating downtime.

It is a still further object of this invention to provide a new and improved pumping arrangement which avoids the need for dynamic seals and bearings in contact with the fluid pumped.

It is still a further object of this invention to provide a new and improved pump design which is of simplified construction, making it economically constructed whereby it is commercially feasible for use in mercury cell units.

Objects in addition to those previously stated will become apparent upon reference to the accompanying drawings and following description of a preferred form of the invention.

IN THE DRAWINGS FIG. 1 is a schematic elevational view of a mercury cell arrangement;

FIG. 2 is an enlarged elevational view, partly in cross section, illustrating the features of the novel pump shown in FIG. 1; and

FIG. 3 is a cross-sectional view taken generally along the line 3-3 of FIG. 2.

Referring now to FIG. 1, the basic elements forming a chloralkali producing system are shown in schematic diagrammatic form. These include a mercury cell 11, decomposer or denuder I2 and pumping arrangement shown generally at 13. In brief, the mercury in substantially pure form enters the cell at the inlet 14, flowing by gravity through the cell and being discharged through line 15 into the decomposer 12 as an amalgam. The spent brine is led off in a known manner.

The passage of the mercury through the cell in thin sheet chamber in a conventional manner while the inlet to the pump fonn beneath a brine solution with a potential applied causes electrolization of the brine solution, releasing chlorine as a gas and forming the amalgam. As noted, the amalgam flows into the decomposer 12 which contains activated carbon and water flowing counter to the flow of the amalgam. The resulting reaction releases hydrogen gas and forms a sodium hydroxide or alkali solution which is tapped off the decomposer. The reaction permits the mercury to revert to its original form, collecting in a thin pool 16 in the bottom of the decomposer 12. A well 17 collects the mercury for flow through a generally U- shaped trap 18 into the pumping assembly 13 of the present invention where it is discharged out return line 20 through the entry inlet 14 of the cell 11. If desired, the trap configuration may be modified to suit individual needs.

As can be appreciated from briefly reviewing the schematic shown in FIG. 1, the quantity of mercury which is circulated through the system is considerable and, for all practical purposes, remains substantially constant. The novel pumping assembly 13 shown in FIG. 1 includes a tank column 21 which is mounted by suitable brackets 22 and 23 to an appropriate structural member which will maintain it in a vertical position at the desired elevation relative to the decomposer tank 13.

At the lower end of the tank column 21 is attached an annular pump casing 24 having a tangential discharge outlet 25. The tank column 21 includes a radial inlet 26 which is connected to the trap 18 to permit gravity flow of the mercury into the tank column. At the top of the pump column 21 is formed a pedestal flange 27 which supports a pedestal assembly 28. The upper end of the pedestal assembly 28 supports a motor 30.

Referring now to the enlarged view of FIG. 2, it can be seen that the tank column 21 has an inner wall 40 which is greater in diameter than the pump impeller 41 which is positioned for rotation in the pump casing 24 on the threaded end 51 of a pump shaft 42 and secured by a jam nut 52. The shaft 42 extends through the tank column 21 and is supported by bearing assemblies 43 and 46 in the pedestal assembly 28. The bearing assembly 43 may be of any suitable design and serves primarily to support the shaft for coaxial rotation. The upper end of the pump shaft 42 may be threaded as at, receiving a nut 45 which serves to support the pump shaft 42. The bearing assembly 46 provides axial as well as radial support for the shaft 42. A suitable coupling 47 is provided on the upper end of the shaft 42 to permit attachment to a cooperating coupling 48 carried on the motor shaft 50. Obviously, if desired, the pump shaft 42 may be formed integral with the motor shaft 50, eliminating the need for couplings 47 and 48 and permitting the overall height of the assembly 13 to be reduced. In such event, the bearings 43 and 46 may be omitted, as the lower motor bearing will be located adjacent the flange 27 on the tank column 21 through a mounting adapter.

The pedestal assembly 28 is provided with a flange 54 at its lower end for cooperation with the flange 27 on the tank column 21. The flange 54 supports an inner column or sleeve 55 through a flange 56 supported by bolts (only one shown) 57. A seal 59 prevents leakage around the circumference of the shaft 42 if the level should rise, however, is not normally in contact with the liquid.

The inner column or sleeve 55 is coaxially arranged with the shaft and is of generally uniform diameter extending the full length of the tank column 21. At the lower end of the sleeve or inner column 55 is .provided a pair of gusset plates 57 and 58 (FIG. 3), which are welded or otherwise suitably attached to the bottom of the column 55. Any number of gusset plates may be used with each joined at its lower end to an annular ring 60 which forms the upper sidewall of the pump casing 24. The ring 60 may be sealed at its periphery by an O-ring or the like to the casing 24, if desired. As best seen in FIG. 2, the ring 60 forming the sidewall of the casing 24 includes a frustoconical surface 61, coaxial with the shaft 42, which terminates at an opening 62 forming the inlet to the pump chamber for directing the liquid in the tank column 21 to the inlet areas of the impeller 41. The inner column 55 shields liquid in the tank column 21 from the rotational forces of the shaft 42 to assure pumping efficiency and safety. The inlet 26 intersects the tank column 21 slightly above the pump casing, as seen in FIG. 1, to assure gravity flow of mercury into the tank column, as the inlet is located at an elevation slightly above the tank bottom and, thus, the level of mercury shown at 33 will, by gravity, seek at least an equal level in the tank column 21. Where considerable alkali is in the decomposer, the mercury level in the tank column will be higher.

A sealing water having low caustic content fills the tank column and helps to balance against the weight of the alkali and mercury in the decomposer 12. The mercury level may be periodically checked and replenished through the inlet stack 68. Suitable fittings 66 and 67 may be provided to accommodate a gauge glass which permits visual inspection for any deterioration of the relationship of the mercury and sealing water level.

it is to be appreciated that the present invention provides a simplified pumping design in which the entire unit may be removed as a unit and replaced without draining the entire system. To the attainment of this end, the pedestal assembly 13 is detached from the tank column by removing bolts (not shown). The motor 30, pedestal assembly 13, column 55 and casing sidewall 60 together with the shaft 42 and impeller 41 are removed as an integral unit. In units having the impeller mounted on the motor shaft, only the motor mounts need be removed and the entire unit can be removed.

it is to be appreciated that where a considerable number of cells are in use, a reconditioned or replacement unit may be readily available so that, in the event of pump failure for any reason, the entire unit may be readily replaced to minimize downtime. It is customary to periodically clean the impeller and pump chamber and the present invention facilitates this with minimum inconvenience. As noted above, the unique vertical pump arrangement eliminates the need for dynamic seals at the impeller casing or in normal contact with the fluid around the rotating shaft 42 and, thus, eliminating any possibility of loss of mercury. Through this novel vertically disposed pumping arrangement, the volume of mercury required for pumping is considerably reduced when contrasted with acceptable prior art pumping designs. The pump is assured of being always primed. The sleeve 55 serves multiple functions in that it supports the sidewall of the pump chamber, shields the mercury from the rotational forces of the shaft and also shields the shaft from the dynamic forces of the incoming mercury which are considerable because of its density. Even though it is superior to existing designs for use in mercury cells, the present invention, because of its simplicity, can be manufactured and assembled at a cost which permits it to be competitive and economically feasible for use in this appiication.

Upon a consideration of the foregoing, it will become obvious to those skilled in the art that various modifications may be made without departing from the invention embodied herein. Therefore, only such limitations should be imposed as are indicated by the spirit and scope of the appended claims.

I claim:

1. In a mercury cell arrangement where mercury is flowed through a cell into a decomposer and recirculated back to the cell, the improvement comprising a pump arrangement for pumping mercury from said decomposer to said cell, said pump arrangement including a tank column adapted for vertical disposition adjacent said decomposer, a casing at the lower end of said tank column, an impeller mounted for rotation in said casing, an inlet located above said impeller to maintain said casing about and around said impeller filled with mercury acting under force of gravity.

2. The improvement in mercury cell arrangements as defined in claim 1 wherein said tank column extends above said inlet and a diverse solution fills said tank column above the level of said mercury to provide a sealing means to prevent caustic from said decomposer to return to said cell.

3. The mercury cell arrangement of claim 1 wherein said inlet in said tank column is connected to said decomposer through a traplike means.

4. In combination, a mercury cell, a decomposer and pump means to pump mercury from said decomposer to said mercury cell, said pump means comprising a tank column having a pump casing at the lower end thereof, a discharge outlet in said casing, said discharge outlet being connected to said mercury cell, an impeller mounted on a shaft for rotation in said casing, means forming a sidewall in said casing above said impeller, an inlet formed in said sidewall communicating with said tank column, inlet means in said tank column for joining to an inlet line extending from a lower-region of said decomposer to direct said mercury by gravity flow into said inlet and said sidewall for recirculation by said impeller back to said cell.

5. The combination of claim 4 wherein sleeve means sur' rounds said shaft in said tank column, said sleeve means being nonrotatable relative to said tank column thereby to isolate movement of said shaft from said mercury.

6. The combination of claim 5 wherein said sleeve means supports said means forming a sidewall in said impeller casing thereby permitting removal of said impeller casing, impeller shaft and sleeve means as a unit. 

2. The improvement in mercury cell arrangements as defined in claim 1 wherein said tank column extends above said inlet and a diverse solution fills said tank column above the level of said mercury to provide a sealing means to prevent caustic from said decomposer to return to said cell.
 3. The mercury cell arrangement of claim 1 wherein said inlet in said tank column is connected to said decomposer through a traplike means.
 4. In combination, a mercury cell, a decomposer and pump means to pump mercury from said decomposer to said mercury cell, said pump means comprising a tank column having a pump casing at the lower end thereof, a discharge outlet in said casing, said discharge outlet being connected to said mercury cell, an impeller mounted on a shaft for rotation in said casing, means forming a sidewall in said casing above said impeller, an inlet formed in said sidewall communicating with said tank column, inlet means in said tank column for joining to an inlet line extending from a lower region of said decomposer to direct said mercury by gravity flow into said inlet and said sidewall for recirculation by said impeller back to said cell.
 5. The combination of claim 4 wherein sleeve means surrounds said shaft in said tank column, said sleeve means being nonrotatable relative to said tank column thereby to isolate movement of said shaft from said mercury.
 6. The combination of claim 5 wherein said sleeve means supports said means forming a sidewall in said impeller casing thereby permitting removal of said impeller casing, impeller shaft and sleeve means as a unit. 